This invention relates to fluid displacement apparatus, and in particular to fluid compressor units of a scroll type.
Scroll type fluid displacement apparatus are well known in the prior art. For example, U.S. Pat. No. 801,182 disclosed a scroll-type fluid displacement including two scroll members each having a circular end plate and a spiroidal or involute spiral element. These scroll members are maintained angularly and radially offset so that spiral elements interfit to make a plurality of line contacts between both spiral curved surfaces, thereby to seal off and define at least one pair of fluid pockets. The relative orbital motion of the two scroll members shifts the line contact along the spiral curved surfaces and, therefore, the fluid pockets change in volume. The volume of the fluid pockets increases or decreases dependent the direction of the orbital motion. Therefore, the scroll type fluid displacement apparatus is applicable to compress, expand or pump fluids.
In a conventional refrigerant compressor, a charge of refrigerant fluid and lubricating oil is introduced. The fluid is compressed by the orbital motion of a scroll member and the compressed fluid is fed out of compressor unit to an external fluid circuit. Lubricating oil is splashed up in the interior of the compressor housing to lubricate desired components of compressor. The splashed up lubricating oil mixes with the fluid and flows out of the compressor unit with the compressed fluid. The part of lubricating oil which flows out of the compressor unit with the compressed fluid adheres to the inner surface of ducts in the external fluid circuit.
It is desirable in the operation of such a compressor unit that the amount of lubricating oil circulating in the compressor be appropriate for the compressor operating speed. Moreover, it is genrerally desirable to utilize a minimum amount of lubricating oil and to minimize the discharge or outflow of lubricating oil from the compressor unit to the external fluid circuit. The reduction of the oil discharge increases the operating efficiency of the condenser or evaporater of the heat exchanger with which the compressor is used.